1. Field of the Invention
This invention relates generally to the field of vascular prostheses and the preparation of these prostheses for implantation in the body of the patient. In particular, this invention concerns a method and kit for harvesting endothelial cells from donor blood vessel, and for inoculating the vascular prosthesis with these cells to facilitate acceptance of the prosthesis within the body.
2. Description of the Prior Art
In the practice of vascular surgery, defects in the vascular system, such as aneurysms or occlusions, are corrected by the technique of suture anastomosis, by which the affected area is excised or resected, and replaced by a prosthetic vascular graft which is implanted and sutured in place. One problem with the use of prosthetic vascular grafts is that the surface of the grafts are thrombogenic and unstable unless covered by endothelium. If blood flow through the graft is compromised, even momentarily, a complete occlusion of the graft may result. The addition of the endothelial lining produces a graft that is non-thrombogenic and is capable of repair and renewal.
The endothelial cells used to inoculate, or seed, the prosthetic vascular graft are extracted, or harvested, from a donor vein of the patient receiving the graft. In the past, the procedure for harvesting the endothelial cells involved inverting a segment of a donor vein of the patient, typically the jugular vein. In this method, the donor vein is turned "inside-out" over a rigid rod. The vein is immersed consecutively into a pair of enzyme solutions that break the bond between the single layer of endothelial cells and the underlyinq cells of the vein. Once the cell bonds are broken, the inverted vein is spun in medium so that the endothelial cells are separated from the vein by centrifugal force. The cells are resuspended and are used to inoculate the prosthetic graft. This procedure has been described in Stanley, Burkel, et al., Biologic and Synthetic Vascular Prosthesis, 1982, ch. 38 "Endothelial Seeding of Enzymatically Derived and Cultured Cells on Prosthetic Grafts".
A double enzyme process has been used to extract the endothelial cells from the donor vein. The donor vein is incubated in a first enzyme, such as trypsin, which is used to break the junctions between the endothelial cells. The vein is then immersed in a second enzyme, such as collagenase, which then infiltrates between the endothelial cells to attack the bonds with the underlying vein tissue.
One difficulty in the prior method has been that the procedure is time consuming, frequently lasting nearly two hours between extraction of the donor vein until preparation of the seeded prosthetic vascular graft for insertion into the patient. Another problem is that the cell harvesting is performed in a laboratory apart from the operating room, thus necessitating that the donor vein be transported outside the sterile environment of the O.R.
The prior method is also cumbersome in that the donor vein must be transported to the laboratory and the endothelial cell suspension must be transported back to the O.R. Inverting the donor vein and using two enzymes to extract the cells also contributes to the cumbersome nature of this method.
One purpose of the present invention is to provide a kit and a method for harvesting endothelial cells and seeding a prosthetic vascular graft that can be performed quickly and efficiently within the operating room. Another purpose is to provide a method and kit for practicing the method that is simple, leaving little room for error or contamination.